The present invention relates to a discharge tube which is capable of changing a luminous color and a discharge device employing the same, and can be, for example, applied to an illuminating lamp, a neon sign, a display lamp and the like which are installed indoors and outdoors.
It has heretofore been considered that the luminance color accompanying gas discharge is uniquely determined in correspondence to the kind of the gas (including vapor) and thus it is impossible to change the luminous color.
On the other hand, one of the present inventors invented a method wherein pulsed discharge is generated using a discharge tube of normal type, and the width, period, rise time and the like of the pulse are changed to control the electron energy within the discharge tube, thereby to change the luminous color of a positive column to change the luminous color of the discharge tube (refer to JP-B-53-42386 and Papers of Technical Meeting on Plasma (No. EP-73-2) entitled "Control of Luminous Color of Discharge" by Ryohei Itatani et al. issued on Jun. 25, 1973 by THE INSTITUTE OF ELECTRICAL ENGINEERS OF JAPAN). In this method, however, since the pulsed discharge is utilized to change the width, period, rise time and the like of the pulse, there arises problems in that a special power source is required, large noise occurs, the power efficiency is reduced, and the loads on the electrodes are large.
Incidentally, the above method is based on a stand-point in that since the luminous color of the discharge tube depends on only the luminous color of the positive column, and the light emission from the negative glow can not be utilized for the luminous color of the discharge tube, the rays radiated from the negative glow should be blocked off as much as possible so as not to leak out.